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/**
* @file configuration.c
*
* @brief Implementation of configuration_t.
*
*/
/*
* Copyright (C) 2006 Martin Willi
* Hochschule fuer Technik Rapperswil
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
#include <stdlib.h>
#include <math.h>
#include "configuration.h"
#include <library.h>
/**
* Timeout in milliseconds after that a half open IKE_SA gets deleted.
*/
#define HALF_OPEN_IKE_SA_TIMEOUT 30000
/**
* Retransmission uses a backoff algorithm. The timeout is calculated using
* TIMEOUT * (BASE ** try).
* When try reaches TRIES, retransmission is given up.
*
* Using an initial TIMEOUT of 4s, a BASE of 1.8, and 5 TRIES gives us:
*
* | relative | absolute
* ---------------------------------------------------------
* 4s * (1.8 ** (0 % 5)) = 4s 4s
* 4s * (1.8 ** (1 % 5)) = 7s 11s
* 4s * (1.8 ** (2 % 5)) = 13s 24s
* 4s * (1.8 ** (3 % 5)) = 23s 47s
* 4s * (1.8 ** (4 % 5)) = 42s 89s
* 4s * (1.8 ** (5 % 5)) = 76s 165s
*
* The peer is considered dead after 2min 45s when no reply comes in.
*/
/**
* First retransmit timeout in milliseconds.
* Timeout value is increasing in each retransmit round.
*/
#define RETRANSMIT_TIMEOUT 4000
/**
* Base which is raised to the power of the retransmission count.
*/
#define RETRANSMIT_BASE 1.8
/**
* Number of retransmits done in a retransmit sequence
*/
#define RETRANSMIT_TRIES 5
/**
* Keepalive interval in seconds.
*/
#define KEEPALIVE_INTERVAL 20
/**
* retry interval in seconds.
*/
#define RETRY_INTERVAL 30
/**
* jitter to user for retrying
*/
#define RETRY_JITTER 20
typedef struct private_configuration_t private_configuration_t;
/**
* Private data of an configuration_t object.
*/
struct private_configuration_t {
/**
* Public part of configuration_t object.
*/
configuration_t public;
};
/**
* Implementation of configuration_t.get_retransmit_timeout.
*/
static u_int32_t get_retransmit_timeout (private_configuration_t *this,
u_int32_t retransmit_count)
{
if (retransmit_count > RETRANSMIT_TRIES)
{
/* give up */
return 0;
}
return (u_int32_t)
(RETRANSMIT_TIMEOUT * pow(RETRANSMIT_BASE, retransmit_count));
}
/**
* Implementation of configuration_t.get_half_open_ike_sa_timeout.
*/
static u_int32_t get_half_open_ike_sa_timeout (private_configuration_t *this)
{
return HALF_OPEN_IKE_SA_TIMEOUT;
}
/**
* Implementation of configuration_t.get_keepalive_interval.
*/
static u_int32_t get_keepalive_interval (private_configuration_t *this)
{
return KEEPALIVE_INTERVAL;
}
/**
* Implementation of configuration_t.get_retry_interval.
*/
static u_int32_t get_retry_interval (private_configuration_t *this)
{
return RETRY_INTERVAL - (random() % RETRY_JITTER);
}
/**
* Implementation of configuration_t.destroy.
*/
static void destroy(private_configuration_t *this)
{
free(this);
}
/*
* Described in header-file
*/
configuration_t *configuration_create()
{
private_configuration_t *this = malloc_thing(private_configuration_t);
/* public functions */
this->public.destroy = (void(*)(configuration_t*))destroy;
this->public.get_retransmit_timeout = (u_int32_t (*) (configuration_t*,u_int32_t))get_retransmit_timeout;
this->public.get_half_open_ike_sa_timeout = (u_int32_t (*) (configuration_t*)) get_half_open_ike_sa_timeout;
this->public.get_keepalive_interval = (u_int32_t (*) (configuration_t*)) get_keepalive_interval;
this->public.get_retry_interval = (u_int32_t (*) (configuration_t*)) get_retry_interval;
return (&this->public);
}
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